(A) Field of the Invention
The present invention relates to a package structure of a compound semiconductor device and fabricating method thereof, and more particularly, to a thin package structure and fabricating method of a photoelectric semiconductor device.
(B) Description of the Related Art
Because the light emitting diode (LED) pertaining to the photoelectric device has advantages of a small body, high efficiency and long life, it is expected to be an excellent illumination source into the next generation. In addition, LCD (liquid crystal display) technology is developing rapidly and full color is the current trend in electronic product displays. Therefore, white series LEDs are not only applicable to indication lights and large size display screens but also to most consumer electronic products such as mobile phones and personal digital assistants (PDA).
FIG. 1 is a schematic cross sectional diagram of the conventional SMD (surface mount device) of an LED device. An LED die 12 is mounted on an N-type conductive copper foil 13b covering an insulation layer 13c through die bonding paste 11, and is electrically connected to a P-type conductive copper foil 13a and the N-type conductive copper foil 13b through metal wires 15. The assembly of the P-type conductive copper foil 13a, N-type conductive copper foil 13b and insulation layer 13c is on a substrate 13. Furthermore, a transparent encapsulation material 14 covers the substrate 13, metal wires 15 and die 12 so that the whole LED device 10 can be protected against damage from environmental and external forces.
The LED device 10 utilizes a common printed circuit board (PCB) as the substrate 13. The total thickness of the LED device 10 is limited by the insulation layer 13c of the substrate 13, and thus cannot be reduced further. However, the current trend of consumer electronic products is toward lightweight, small packages. Accordingly, each of the internal devices of the consumer electronics product and its shell needs to be miniaturized. On the other hand, the insulation layer 13c is made mostly of epoxy resin with poor heat dissipation, and therefore is not suitable for a high power chemical compound semiconductor as a heat-transferring path.
FIG. 2 is a schematic cross sectional diagram of a high integral package structure disclosed by U.S. Patent Publication No. 2004/0090756. The package structure has an insulating layer coated on a temporary substrate, and has electrical circuits which have been previously designed and laid out on the insulating layer. Subsequently, LED dies 221 and 222 are adhered to a substrate 23, and the LED dies 221, 222 and the internal leads of the substrate 23 are connected to each other through metal wires 25 by the wire bonding (or through bumps by flip-chip bonding). Conventional epoxy resin covers the LED dies 221 and 222 by using a molding process. In order to reduce the thickness of the whole package, the temporary substrate is removed from the insulating layer by the illumination of laser light or UV light. Tin balls 26 are soldered to the default soldering pads. Thus, a highly integral and thinner package is obtained. However, the manufacturing processes of the package are complicated so that the cost of manufacture is high.
In view of the above, the consumer electronics market is in urgent need of a photoelectric compound semiconductor device with a thin type package. The device not only needs to have a reduced thickness for saving space, but also needs to address the heat dissipation problem. With such a device, reliable, high power electronics products which can be more easily manufactured.